The present invention relates to a solid electrolytic capacitor used in various electronic devices, and to a method of manufacturing the capacitor.
FIG. 11 is a sectional view of a conventional solid electrolytic capacitor disclosed in Japanese Patent Laid-Open Publication No.2000-243665. One side or a middle core portion in a thickness direction of porous valve metal sheet 20 made of metal, such as aluminum and tantalum, is used as an electrode. Dielectric layer 21 is provided on a surface of a porous portion of the valve metal sheet 20. Solid electrolyte layer 22 formed of a conductive polymer layer is provided on the dielectric layer 21. Collector layer 23 is provided on the solid electrolyte layer 22. An electrode layer made of metal is provided on the collector layer 23.
When the solid electrolyte layer 22 is formed in this solid electrolytic capacitor, conductive polymer is formed at electrode lead-out portion 24 of the valve metal sheet 20, thus causing a short-circuit or a current leaking. In order to prevent such trouble, the electrode lead-out portion 24 is separated from the solid electrolyte layer 22 with insulating separator 25 made of insulating resin provided at the electrode lead-out portion 24.
The insulating separator 25 is generally formed by applying and hardening insulating resin, such as epoxy resin and silicone resin, or by affixing an insulating tape including polyamide as a base material. The solid electrolyte layer 22 becomes partially defective on the dielectric layer 21 close to the boundary between the dielectric layer 21 and the insulating separator 25, and this may cause a short-circuiting or a current leaking.
When insulating resin is applied, the resin is sucked into the porous portions of the valve metal sheet 20, and thus, the capacitor becomes unable to control its electrostatic capacity, losing its characteristics as a capacitor. Further, the application of insulating resin influences workability and mass-productivity in a manufacturing of the capacitor.
A solid electrolytic capacitor includes a valve metal sheet having a porous portion on a first surface of the sheet, a dielectric layer provided on the porous portion, a first insulating portion provided on an outer periphery of the dielectric layer, a solid electrolyte layer provided on the dielectric layer, a second insulating portion provided on an outer periphery of the solid electrolyte layer and on the first insulating portion, and a collector layer provided on the solid electrolyte layer.
The solid electrolytic capacitor causes less current leakage and assures a high withstand voltage.